Archiving earlier versions of CRUTEM

About CRUTEM

CRUTEM is a dataset derived from air temperatures near to the land surface
recorded at weather stations across all continents of Earth. It has been developed
and maintained by the Climatic Research Unit since the early 1980s, with funding
provided mostly by the US Department of Energy. The lead scientist for most of this
work was Professor Phil Jones, though many colleagues have also contributed. In
recent years, the Met Office Hadley Centre (MOHC) have also been involved, especially in
the regular updating of the operational version of CRUTEM (current version CRUTEM4).
CRUTEM has been combined with the MOHC's dataset of sea surface temperatures to provide
a near-global dataset of temperatures across Earth's surface, called HadCRUT. For example,
the current version HadCRUT4 combines CRUTEM4 and HadSST3. These datasets have been
widely used for assessing the possibility of anthropogenic climate change.

The latest version of CRUTEM is available at the
Climatic Research Unit and at the
Met Office Hadley Centre.
The ACRID project focussed on publishing CRUTEM3, including the workflow from station
data to gridded and global datasets, according to the linked-data method.

As an additional outcome of the ACRID project, we have also been able to assemble an
archive of some earlier versions of CRUTEM, as reported by Osborn and Jones (2014).
If you find these earlier versions of CRUTEM
useful, then please acknowledge this work by citing:

Uniquely identifying CRUTEM versions

After each major version of CRUTEM has been adopted as the current operational
version (e.g. CRUTEM3 was adopted in 2006), it is updated each month. Each update adds an extra
month's data to the end of the series, but also includes any late reported data for previous months
and even previous years. Occasionally, changes affecting earlier values have also been
made to correct errors that have been identified or to improve the homogeneity of the series.
Each month, therefore, a new version of CRUTEM is generated. Roughly once per year, more
extensive revisions to the database are made, and sometimes modifications to the algorithms
are also made.

For most purposes, it has been sufficient to identify the version of the dataset that has been
used in a particular study by the major version number (e.g. CRUTEM3) together with the appropriate
reference. In some cases, it might be valuable to be able to identify a specific monthly update
of the dataset; for instance, if it is necessary to identify the precise version used so that a
particular published analysis can be repeated exactly.

Until recently, individual monthly updates of CRUTEM have not been uniquely identified.
MOHC introduced a version numbering system
when CRUTEM4 was released, which is updated when significant modifications to the data and/or algorithm are made.
This can be combined with the labelling used in this archive,
where we recommend that every monthly update can be uniquely labelled using an identifier
that combines the major 'version' with the date corresponding to the latest data contained in the data file.
Hence, a file containing data that run through to include values to the end of May 2011 would be labelled
CRUTEM3-2011-05. Note that this is not the version that was created
in May 2011 because that will likely have data that run through to only the end of April 2011 (and would be
identified as CRUTEM3-2011-04). Updated versions are usually created 3 to 4 weeks after the end of the month.

An archive of CRUTEM versions

The earlier versions of CRUTEM (gridded and global/hemispheric means) that are currently available
are linked to in the table below. These versions have been obtained from a number of sources, whose
support is acknowledged, especially the
Internet Archive's Wayback Machine.

Caveats. We cannot guarantee that the assignments of particular files to particular monthly versions
is completely accurate. These have been recovered and/or recreated from various archives and because
unique identifiers had never been attached to each monthly update, there is some uncertainty in assigning
these files to particular monthly versions. If you identify errors or have additional or different older
versions of a CRUTEM dataset, then you are welcome to contact Tim
Osborn.

The formats of these datafiles have varied over time. Please refer to the CRU and MOHC websites for
details of some of the formats that have been used.

CRUTEM1

Note that the dataset was not called this at the time, but it has been retrospectively named as
CRUTEM1.Reference: Jones PD (1994) Hemispheric surface air temperature variations: a reanalysis
and an update to 1993.
Journal of Climate7, 1794-1802.